TIM GANNON FILE PHOTO | Route 24 in Riverside, where a new ‘Main Street’ is envisioned.

New technologies in wastewater treatment could allow a small sewer plant to be built in Riverside for just $2 million — infrastructure that would be key to advancing efforts to transform a blighted stretch of Route 24 into a bustling main street and revitalize the surrounding area, says Suffolk County Legislator Jay Schneiderman (I-Montauk).

GRAPHIC COURTESY JAY SCHNEIDERMAN | The footbridge that will cross the Peconic River and connect Riverside to downtown Riverhead.

Mr. Schneiderman also says there could be county grant money available to cover a chunk of that cost.

Grant money may also be available for two other proposals Mr. Schneiderman recently made as part of a vision he and town officials share for the beleaguered Riverside hamlet: a walking path to the nearby Peconic River and a footbridge over the river to downtown Riverhead. (See digital rendering on page 28.)

For an area with such a high water table, sewer treatment is necessary for any building improvements, and a traditional sewage treatment plant for Riverside would cost more than $10 million, Mr. Schneiderman said, pointing to Riverhead Town’s sewage treatment plant, which cost $8.75 million to build in 2000. Upgrades to the existing Riverhead plant, needed to satisfy state requirements, are expected to cost upwards of $20 million.

Assemblyman Fred Thiele (I-Sag Harbor) has told the News-Review federal money would be necessary to build a full-scale plant in Riverside, and that such funding has dried up.

The water table and proximity to the environmentally sensitive Peconic River have put huge constraints on most development efforts in Riverside. As a result, most large scale building proposals there have failed and many buildings in the area are now vacant or boarded up.

The grant money Mr. Schneiderman said might be available comes from the county’s quarter-percent sales tax, which raises money for drinking water protection. Each year, $2 million is available for alternative sewer systems — and that money went unused last year, he said, bringing the available total to $4 million.

“I think if you have a low pocket of commercial development, it makes sense to have a small facility to handle it,” he said. “It would need far less land and far less piping. In Riverside, I think it could be done for $2 million.”

In June, Mr. Schneiderman unveiled a 3-D computer graphic “vision” for the area near the Riverside traffic circle at a meeting of the Flanders Riverside and Northampton Community Association.

He proposed creating a new downtown commercial area for Riverside just east of the traffic circle, with three-story mixed use buildings on the south side of Flanders Road, across from McDonald’s; a restaurant at the former Riverboat Diner property; a supermarket where the Budget Host Inn is; a walking path from Flanders Road to the Peconic River; and a footbridge over the river into Riverhead Town.

Mr. Schneiderman’s plan also showed a realignment of the traffic circle as well as one small sewer plant to serve just this small business district. He said other small decentralized plants could be built elsewhere in the future if the business area grows.

“I don’t believe that any of this can unfold without sewers,” he said.

Last year, the county approved a $750,000 grant to fund a study investigating the feasibility of a Riverside sewer district. That study is being conducted by the engineering firm Camp Dresser & McKee and is expected to be complete in the fall.

In the early meetings on the sewer district proposal in 2011, officials were considering a number of options, including a sewer district stretching from Riverside into the Bay View Pines section of Flanders, which would serve homes and businesses.

The likely high cost of that plan led officials to shrink the scope of the project to just the Riverside business district, including the former drive-in site where an industrial park and hamlet center are planned to the east.

But Mr. Schneiderman’s plan covers an even smaller area and seeks to create a Riverside business area in the area by the traffic circle that extends only as far east as Vail Avenue.

The plan showed one small sewage treatment plant, designed to serve only this small area.

Mr. Schneiderman said there are new technologies that allow for smaller “package” plants to serve commercial areas. These include the Membrane Bioreactor (MBR) technology and a system called Nitrex, made by a company in Boston.

Kevin McAllister of Peconic Baykeeper, an environmental watchdog group that has been critical of nitrogen discharge levels into the Peconic Bay system and into groundwater, said in an interview that the Nitrex system is the best he’s seen at removing nitrogen from sewage discharge.

High nitrogen levels will trigger algae blooms, which will lead to low dissolved oxygen levels and fish kills, Mr. McAllister said.

The Peconic River, Saw Mill Creek, Meeting House Creek, Reeves Bay and the western part of Flanders Bay are all considered impaired water bodies by the state because of too much nitrogen, he said. And since the Peconic River is groundwater fed, failing cesspools along the river will eventually lead to pollution of surface waters too, he said.

In the past, the Suffolk County health department has been reluctant to approve alternative sewer systems that remove nitrogen, Mr. McAllister said.

But the health department earlier this year approved four alternative on-site systems for sewage disposal, including Nitrex.

Pio Lombardi, the president of Nitrex, said in an interview last Wednesday that the Suffolk County standard for nitrogen in drinking water is 10 milligrams per liter, but that Nitrex has undertaken projects that brought levels much lower.

“We have a project in Malibu, Calif., in the low 1’s and we know what to do to get it below 1 [MPL],” Mr. Lombardi said. The Nitrex system can be placed under parking lots, which saves money on land acquisition, he said.

Asked if the system would work in areas with high groundwater tables, like Riverside, Mr. Lombardi said his company has installed systems in such areas, but it does increase the construction costs, and a a dewatering system would be necessary.

“We generally need six to eight feet above groundwater, but we can also built them above ground.”

Ben Wright, an engineer with the county Department of Public Works, which also is working on the Riverside study, said at the recent civic meeting that Membrane Bioreactor technology is what Riverhead Town is going to use in its sewer upgrade.

“That’s the best quality you can get,” he said.

Southampton Town, meanwhile, is issuing a request for qualifications from developers, similar to what has been done to help advance revitalizations projects in Wyandanch and around the Ronkonkoma train station, said Southampton Supervisor Anna Throne-Holst

“The municipality would invite developers and businesses to come to us and give us proposals,” she said. This way, she added, improvements could be funded by private developers rather than government funds.

“There are lots of ways to skin this cat,” she said. “Our goal has been to approach as many angles as we can.”

While most of Mr. Schneiderman’s proposals for Riverside come as part of a “vision” and are not actual development proposals, he does have the support of Flanders Riverside and Northampton Community Association members.

“Absent the possibility of linking up with the existing treatment plant at Riverhead, my personal preferred option, I completely support creating a small, modern plant in Riverside to handle only the flow that might be generated along Route 24 in the commercial area,” said FRNCA president Vince Taldone.

Riverhead Town would need additional land it doesn’t have in order to expand its own sewer plant to handle Riverside, said Riverhead Supervisor Sean Walter. In addition, the Riverhead Town Board members serve as commissioners of the sewer district, and Mr. Walter added that he would not support expanding into Southampton Town if it involved giving up that control.

Mr. Taldone said having a sewer system in Riverside “will enable new, higher-water-usage businesses to open and will enable some additional residential development to create a nice mixed-use redevelopment.”

Meanwhile, in other efforts to advance the vision for Riverside, the FRNCA group is seeking $1.45 million in grants to build a footbridge over the Peconic River, connecting county parkland in Riverside to a section of downtown Riverhead near the Long Island Aquarium.

FRNCA also is backing a $50,000 grant application by Southampton Town and Suffolk County to create a walking trail from Flanders Road to the section of the riverfront where the bridge would go, should it get to that point.

Both proposals are elements of a 3D computer graphic “vision” for Riverside unveiled by Mr. Schneiderman at a June 10 FRNCA meeting.

Mr. Taldone, said the group applied for New York State Economic Development grants for the footbridge.

The area where the foot path is proposed was once part of a 20-acre site proposed for a hotel and convention center by Southampton Inn owner Dede Gotthelf in 2001. Ms. Gotthelf’s plan ran into numerous obstacles, and she ended up selling all but about six acres to Suffolk County as open space.

While that land is now considered parkland, Mr. Taldone said it’s still largely inaccessible to the public.

“People in Riverside can’t get down to the water without climbing through the weeds,” he said.